John Manix PE PTOE Neighborhood Traffic Engineer, City of Vancouver, WA
Figure 1. Evergreen Boulevard before the project in area of speed cushions.
Evergreen Boulevard serves as a popular bike route with great potential as a bike commuter route. It was rated by the Cycle Clark County Map as having a low level-of-service for bikes. Its roadway classification is collector with an average daily traffic of 3200 vehicles per day. It connects between downtown and a large residential neighborhood. The width is 9.8 m (32 ft), with parking allowed on one side before the project (figure 1). It has commercial bus service that serves both blind and deaf students in the area.
The street was an old state highway before the construction of Washington SR 14 and still provides access to the City’s Historic Reserve.
Community goals for the project were to improve bicycle safety and compatibility, pedestrian access for persons with disabilities, to slow traffic, and to enhance the roadway aesthetics with the hope of spurring redevelopment.
The work on the corridor was broken down into phases. This report focuses on Phase 1 from E. Reserve to Grand Boulevard.
Speeding on Evergreen Boulevard was a common neighborhood complaint with the speed posted at 25 mph. The 85th percentile speed was 34 mph, with about 90 percent of the vehicles traveling over the speed limit.
The phase 1 section of Evergreen Boulevard is 0.65 miles long and had relatively few collisions. In the three years before construction, 20 collisions were reported with the majority (12) at Grand Boulevard. The majority of the collisions at Grand Boulevard were “approach turn” collisions related to Grand Boulevard traffic, not Evergreen Boulevard. Most of the other collisions were at minor intersections and were of the “right angle” type. No bike or pedestrian collisions were reported along Evergreen Boulevard in the phase 1 section.
The surrounding and adjacent neighborhood associations had identified a goal of creating a bicycle path along Evergreen Boulevard in their Neighborhood Action Plan.
Installation of a path was infeasible, so the alternatives were to install bike lanes, place signs along a bike route, or improve an alternative route.
The project scope proposed installation of bike lanes on Evergreen Boulevard, but this required removal of all on-street parking. Removal of parking is never popular, particularly on this section with commercial land use. Knowing parking restriction would not be popular, staff proposed installation of bike lanes and “streetscape” improvements to minimize the protests associated with the loss of parking. The streetscaping was supported by the local neighborhood association because it reinforced the goal to beautify the street.
After extensive public involvement, the consensus was to install bike lanes on most of Evergreen Boulevard but to leave 26 on-street parking spaces for three blocks in the commercial district. To enhance bicycle compatibility in this section with shared travel lanes and on-street parking, traffic calming was proposed. Traffic calming also addressed resident concerns with speeding on Evergreen Boulevard.
The traffic-calming tool of choice was then an important consideration. Typical speed humps were ruled out based on the impacts to commercial transit service and fire department response time. The use of certain traffic calming measures was controversial with bicyclists because of safety concerns. A previous traffic-calming project on a popular bike route used curb extensions that generated many bicycle safety complaints associated with bike riders being pinched between moving traffic and the curb extensions.
Staff had, for some time, considered the use of “speed cushions” as an alternative to speed humps to provide an effective traffic-calming tool on arterial, collector, or local streets that serve as emergency response routes.
Speed cushions are modified speed humps. The shape resembles a cushion or pillow placed in the roadway, but a speed cushion does not span the entire roadway or traffic lane. The intent is to slow most motor vehicles, similarly to a speed hump, but to allow wide wheel-based vehicles such as buses and fire trucks to drive over them with minimal impact, as cushions are narrower than the wheel base of these vehicles.
In researching the topic, staff found speed cushions in use in the United Kingdom as early as 1993 and learned of American experience in the cities of Sacramento, CA, and Austin, TX. Sacramento’s experience with what they refer to as a “speed lump” was particularly important because these devices are designed for the same size of fire engine and commercial bus as used in Vancouver. Figure 2 illustrates the trial speed lump from Sacramento.
Figure 2. Sacramento speed lump.
Figure 3. Trial rubber speed cushion.
Vancouver tested speed cushions using rubber speed hump components that could be assembled to match the Sacramento speed lump width dimension of 1.8 m (6 ft) (see figure 3).
These trials allowed the City to test several configurations related to the position of speed cushion in the street. For example, should one cushion be placed in the center of the roadway like Sacramento’s speed lump, or should they be placed in the center of the travel lane? If in the lane, how far apart should adjacent cushions be?
With the fire department’s endorsement of the rubber speed cushion, the City implemented two other traffic calming projects concurrently with the Evergreen Corridor bike lane project that used speed cushions. These projects were West 33rd Street from Main Street to Columbia Street, and Southeast 155th Avenue from Southeast Mill Plain Road to Southeast 1st Street. They were only intended to slow traffic and were not intended as bike improvements. The before and after speed survey data from the three projects as well as one other is provided in the evaluation.
Before and after bike counts were collected, compared and found inconclusive. The pre-project Evergreen Boulevard bike volumes were about 1 percent of the total traffic as measured in the midweek afternoon peak hour. The after volume was about the same but at this small a sample size, the staff does not feel confident that the results can be attributed to the project.
The Bicycle Compatibility Index: A Level of Service Concept (Bicycle LOS) by FHWA was used to evaluate the projects’ effects on bicycling on Evergreen Boulevard. This method is straightforward and matches local experience. In previous work, staff found that this evaluation tool approximately matched the evaluation used by the Clark County Bicycle Advisory Committee’s Bike Map (Cycle Clark County) that independently rated roadways for bicycle compatibility. The Bicycle LOS evaluation included comparing the shared lane with parking on one side of Evergreen Boulevard section before and after the speed cushions were installed, and also that of the section with bike lanes and no parking allowed.
The secondary performance measures were related to community goals not exclusively linked to bicycling. The neighborhood hoped for a reduction in speeding. This objective was evaluated with a before and after speed survey, a traffic count, and a collision history review. The speed survey and traffic count data were collected via hose counters in the vicinity of the proposed traffic calming before and midway between speed cushions following installation. The traffic data were collected for one midweek day. This report includes the results of three other speed cushion projects to evaluate the effectiveness of this relatively new traffic calming tool.
Staff anticipated a collision reduction associated with the traffic calming. The city’s collision database was queried for three years before and one year after the project was implemented.
City staff hoped the speed cushions would demonstrate a bicycle, fire truck, and transit-friendly speed hump design. To evaluate these objectives, staff solicited comments from local bike club members, the local transit agency and the fire department.
The results of installing speed cushions in the section of Evergreen Boulevard with parking improved the Bicycle Level of Service or Compatibility, but not nearly as much as the section with bike lanes and no parking. Table 1 shows the results of the Bicycle LOS evaluation.
|Midblock Identifier||BCI||Level of Service||Bicycle Compatibility Level|
|Evergreen Boulevard - Before Project EB without Parking||3.47||D||Moderately Low|
|Evergreen Boulevard - Before Project WB with Parking||3.47||D||Moderately Low|
|Evergreen - After Project with bike lanes & no parking||1.97||B||Very High|
|Evergreen - After Project WB with Parking||3.24||C||Moderately High|
|Evergreen - After Project EB without Parking||3.24||C||Moderately High|
The LOS changed from a high D to a mid-level C with the addition of speed cushions. This minor change is significant because LOS of C is noted in The Compatibility Index: A Level of Service Concept, Implementation Manual as a bench mark for roadways where casual bicyclists are expected. As a popular recreational bikeway, this is a reasonable expectation for Evergreen Boulevard.
The Bicycle LOS of B for the bike lane section confirms staff efforts to keep the shared lane section as short as possible.
The Bicycle LOS evaluation looked at the before and after traffic data, noting changes in traffic volume, speed and parking occupancy of the on-street parking. The Bicycle LOS was calculated for each direction because parking was allowed on one side only. But parking had little impact on the Bicycle LOS because the occupancy rate is low (less than 25 percent) both before and after the project.
In all cases, the speed cushions significantly reduced the speed of vehicles and have likely reduced the number of collisions. Table 2 shows the results of the speed survey and collision history of the four streets with speed cushions. All locations had very consistent results.
|Roadway with Termini||Traffic Collisions per yr||Daily Traffic Volume||85% Speed||Percentage of Vehicles Over 30 MPH|
|Evergreen Boulevard; X St to Winchell — Before||1.25||3,900||34 MPH||42%|
|Evergreen Boulevard; X St to Winchell — After||0||3,400||29 MPH||8%|
|W 33rd St; Washington to Columbia — Before||NA*||3,300||33 MPH||19%|
|W 33rd St; Washington to Columbia — After||0||3,000||29 MPH||7%|
|SE 155th Ave; Mill Plain to SE 1st St — Before||0||3,400||34 MPH||37%|
|SE 155th Ave; Mill Plain to SE 1st St — After||0||3,100||28 MPH||9%|
|NE 49th St: NE 26th St to Work St — Before||.33||1,500||35 MPH||44%|
NE 49th St: NE 26th St to Work St — After
* This location had speed humps changed to speed cushions to address fire department concerns with response delays associated with humps.
The 85 percent speed is at or slightly lower than 30 mph on all streets that have a 25 mph speed limit. More importantly, the percentage of vehicles over 30 mph dropped dramatically (see table 2).
The traffic volume on each of the streets with speed cushions dropped about 10 percent. This traffic diversion could cause complaints on parallel routes, but no complaints have been received.
None of the four sites had a significant number of collisions in the three years before the project. One year after the installation of speed cushions, there are encouraging, but inconclusive results with no collisions since installation (see table 2).
The following information was gained from the trial with rubber humps and permanent installation of four projects:
Figure 4. Speed cushion design configuration for 36–38 ft streets — use with parking restrictions.
Figure 5. Fire engine over speed cushion — too close to parked vehicle.
Figure 6. Speed cushion design with pavement marking.
Figure 6 shows the speed cushion with pavement marking detail that is in compliance with the MUTCD ME.
Our striping crew has added the same pavement marking on the additional hump which spans the shoulder-parking area to the right of the speed cushion. This marking is technically incorrect but conforms with past practice used by many agencies that use an arrowhead-type marking on humps.
The first comments regarding the speed cushions on Evergreen Boulevard from Vancouver Bicycle Club (VBC) members were negative because the speed cushions were initially installed incorrectly, making them uncomfortable to ride over. This was true for both cars and bikes. They also objected to them because of concerns with loss of control and apparent lack of need. After the modifications, the City received the following comment from a member of VBC:
“Bicyclist” stopped in to tell you that you that Evergreen Boulevard is “wonderful.” He was very pleased with the speed bumps being “redone.” We also have received positive comments regarding the bicycle improvements on the corridor.
Comments related to transit have been very positive. The C-Tran representative commented:
Thanks for the information that you provide; it was very helpful. I checked with the current operators driving through Evergreen Boulevard and have not had any negative feedback. In fact, the cushions seem to be allowing them the ability to travel through with limited interference. They appear to be “transit-friendly” with the most recent adjustments.
Another comment from a City Council member to the City Manager:
While on the same bus trip with the Japanese kids I referenced earlier, we took Evergreen eastbound. (It looks absolutely GORGEOUS.) The bumps were no problem for the driver. In fact, he said that they were so much better than Portland’s. That was Evergreen Coach that took us. Big bus, not uncomfortable at all.
Fire department staff gave positive comments on the speed cushions several times. The quality of the ride on Evergreen is relatively poor because of dips at cross streets, so it is not an important response route. The West 33rd Street traffic calming project demonstrated that the fire engine drivers need ample clearance (0.9 m (3 ft) or more) with parked cars to traverse the speed cushion at full speed.
The staff has taken several comments from the public regarding the lack of effectiveness of the speed cushions. The comments are generally related to comparison with speed humps and can be paraphrased as: “I can drive over those humps at a high rate of speed.” But the speed data do not support that opinion.
Adding speed cushions to Evergreen Boulevard increased the Bike LOS to a level (C) that will accommodate recreational riders expected on this facility, and allowed the city to address the desire of the commercial community to maintain on-street parking. But if parking had significantly increased, the lower speeds and volumes would not have adequately compensated to keep the Bicycle LOS to C. The Bike LOS evaluation methodology is more sensitive to changes in parking than the speed of traffic.
Thus the use of speed cushions is not recommended as a replacement for bike lanes for long sections of roadway, but they are a valuable tool in assuring that the total project was a success in accommodating multiple interests – in this case the businesses that valued parking, bicyclists that needed safe bicycle facilities, and transit and emergency response. Speed cushions are relatively new traffic calming tools that appear to be successful at calming collectors or arterials that serve both as fire response and transit routes and carry moderate levels of bicycle traffic.
Traffic calming remains controversial with some bicycle riders. The main concern with speed cushions relates to loss of control by hitting the tapered side of the speed cushion near the gutter. If the speed cushion design can provide a clear wheel path through the speed cushion, this safety concern would be addressed. On future projects with bike lanes the city plans to modify the design to minimize the risk that bicyclists will traverse the speed cushion on the tapered side.
The use of traffic calming on streets classified as “collector” will always be controversial. If time proves speed cushions to be a successful traffic calming tool, we must be wary of overuse. A likely negative outcome of overuse is diversion of traffic onto parallel residential streets. In the past, increases in emergency response time and the high cost of alternative traffic calming tools have limited deployment. Because speed cushions address these issues, adoption of policies to prevent a slippery slide of overuse is recommended. The policy should limit the use on collectors to bracketing important crosswalks, parks, schools or short sections of parking on bike routes.
Speed cushions (material and labor): $2,000 each
Funded within a larger project included a Federal Transportation Enhancement grant and local matching funds.
John Manix P.E. PTOE
City of Vancouver
PO Box 1995
Vancouver, WA 98668-1995
City of Vancouver
PO Box 1995
Vancouver, WA 98665-1995